Electromechanical razor operable at high frequencies



B. R. MEAD May 5, 1970 ELECTROMECHANICAL RAZOR OPERABLE AT HIGHFREQUENCIES 5 Sheets-Sheet 1 Filed March 11, 1968 INVENTOR Bruce R. MeadBY 47mm? r1 ATTORNEYS y 5, 1970 B. R. MEAD 3,509,626

ELECTROMECHANICAL RAZOR OPERABLE AT HIGH FREQUENCIES Filed March 11,1968 I 3 Sheets-Sheet 2 FIG. 3

INVENTOR Bruce R. Mead BY Lind 56M W {ID/4v ATTORNEYS 3. R. MEAD May 5,1970 ELECTROMECHANICAL RAZOR OPERABLE AT HIGH FREQUENCIES Filed March11. 1968 5 Sheets-Sheet 5 FIG.9

FIG. IO

INVENTOR BRUCE R. MEAD ATT'YS.

United States PatentO 3,509,626 ELECT ROMECHANICAL RAZOR OPERABLE. ATHIGH FREQUENCIES Bruce R. Mead, .Fairfield County, Conn., assignor toEversharp, Inc., Milford, Conm, a corporation of DelawareContinuation-in-part of application Ser. No. 431,606, Feb. 10, 1965.This application Mar. 11, 1968, Ser. No. 711,954

Int. Cl. B26b 21/00 US. Cl. 30-45 11 Claims ABSTRACT OF THE DISCLOSUREAn electromechanicalrazor in which transducer means operable at anultrasonic frequency, is mechanically coupled to one end of a razor orlike blade held 1n razor head means, and wherein the vibrational energyof the transducer causes ultrasonic vibrations in the cutting.

blade, In a preferred embodiment, the output of an electronic inverteris fed to a piezoelectric crystal held against a back edge of the blade,and vibrational energy from the crystal is fed to the blade, preferablyin resonance with a natural or imposed frequency thereof, causing theblade, or portions thereof, to vibrate at a frequency of at least about100,000 cycles per second- The power supply, such as the inverter, or anoscillator and amplifier may be contained in, or partially or completelyremote from, the blade support means. Piezoelectric. as well asmagnetostrictive transducers are described.

This application is a continuation-impart of; my earlier filedapplication Ser. No. 431,606, filed Feb. 10, 19.65,

now abandoned.

This invention relates to shaving instruments and more particularly toan electromechanical razor.

Razors having motor-driven cutting edges which describe rotary andoscillatory and vibratory motion have i been in common use foraconsiderable time. These known electromechanical razors have not beenunsatisfactory, but their performance has. left much to be desired. For

3,509,626 Patented May 5, 1970 "ice instrument which is so conceived anddesigned. as to drive the cutting edgeof the blade or other cuttingmeans against the individual hairs with extremely high impact forceswhereby the mechanism by which the hair is several depends in large partupon inertial forces between the hair and the impacting blade and to amuch lesser extentupon the ordinary static forces between the cuttingedge and the relatively immobile hairl anchored in the skin.

According to my invention my new shaving instrument or razor comprisesvibratory cutting means having a cutting edge thereon. I providevibratory electromechanical transducing means coupled to the cuttingmeans and adapted to vibrate the cutting means at ultrasonicyfrequency.The shavinginstrumentor razor according to my invention is also.provided with means for exciting the transducing means at ultrasonicfrequency. The combination of these elementsresults in the edge on thecutting means being forced to vibrate, at ultrasonic frequency suchthat, while the amplitude of vibration may be .very small, 1 theacceleration. andhence, the impact forces:.be-

tween :the cutting edge and a hair are extremely high.

and create highly localized forces in the form of high-frequencyvibrations, shock. waves, local heating and sawing and chiseling actionswhichare coupled to the individual.

my invention;

most persons, shaving is a very personal and individual experience bothphysically and psychologically. What. is a more or less satisfactoryperformance to one person may be quite unsatisfactory to another person.

Out of my experience with shaving instruments of many kinds, it becameapparent to me that most of the known electromechanical shaversgenerally fall short of wholly satisfactory performance because theyhave been designed with a view to duplicatingmore or less closely thefundamental cutting action :of straight edge razors. and

safety razors. Other shaving instruments have been made.

in which the cutting edges of electromechanical razors are vibrated atfrequencies approximating the upper limits of the audio range. Myinvestigations into the mechanical properties of hair and of theessential nature of the mechanism of cutting hair with a blade revealedto me that none of the designs of existing electromechanical shavinginstruments were based on a full understanding of the nature of theproblems involved. The resulting cutting instruments are not capable ofsevering individual hairs while transmitting to the nerve ends in theskin a minimum of the irritating forces which cause stinging and burningsensations during and after shaving.

My investigations have shown that the pressure required to cause aconventional razor blade to sever the hard substance of a human hair isof the same order of magnitude as that required to sever aluminum orcopper in wire form. I have found that this pressure approaches 30,000pounds per square inch. With these and other new facts. at hand, I haveinvented an entirely new shaving FIG. 2 is a front elevation of therazor illustrated {in FIG. 3 is a sectional view taken along the line 33of FIG. 2;

FIG; 4 is an enlargedperspective of the blade driving mechanism for therazor shown in FIGS. 1-3;

FIG. 5 is an enlarged view in section. of a modification of the razorshown in FIGS. 14; and

FIG. 6 is a perspective view of the blade and blade driving mechanismof, the razor shownin FIG. 5;

FIG. 7 is a vertical sectional view taken through a pertion of anotherembodiment of the razor unit of the 'invention showing lthe jbladeandblade support means thereof, wherein flexural mode of transducervibration is used.

FIG. 8 is a sidefview of a crystal unit of the invention, illustratingone mode of vibration thereof;

FIG. 9 is a side view of another type of crystal unit useful in theinvention, showing the mode of vibration thereof. 1 a

FIG. 10 is a schematic drawing showing the operation of an electronicinverter power supply means which is useful .with the present invention.

In FIGS. 1 and2 I have illustrated the external .configuration of arazor embodying my invention. This comprises essentially :a shavinghead. indicated at 1 and a handle indicated generally at 2. It should beunderstood that the external appearance and therelative arrange ments ofthe shaving head and the handle are nota part of the invention. The formillustrated in FIGS. 1 and 2 is simply one convenient form in which thecomponents of the inventionmay be associated. In this particular form,the shaving head ressembles in many respects the external appearance ofa commercially available singleedge safety razors.

The shaving head 1 comprises a frame consisting of upper and lowerplates 3 and 4 which are joined together at the back by the wall 5, thethree components just mentioned being a unitary member in thisembodimerit. As best seen in FIG. 1, the plates are spaced apart towardthe rear to form a housing for components to be described. As is alsoshown in FIG. 1, the plates converge toward the forward part of theframe such that the forward edge 6 of the upper plate 3 converges on thelower plate 4 and is preferably designed so that this forward edge wouldhear on the lower plate but for the interposed blade indicatedat 7.

On the forward edge of the lower plate 4 there is a conventional guardbar 8 which assists in positioning the cutting edge of the blade 7 inrelation to the skin during shaving. At the opposite ends of the guardbar there are blade stops 9.

The shaving head 1 is joined to the handle 2 by a neck 10 which may beforced as an integral part of the shaving head 1. The handle may beformed of any suitable material such as a cast or molded synthetic resinand may be provided with knurling as indicated at 11 to give anattractive appearance and to provide non-slip 12 and the driving edge13whichis preferably at or near a vibrational node. The significance ofthis will be described in greater detail below.

Within the space between the upper plate 3 and the lower plate 4 to therear of the driving edge 13 of the blade, there is located anelectromechanical trans ducer which in various embodiments maybeaquartz,

barium titanate, or other like crystal 16, or a ceramic materialdescribed further herein. The crystal is cut so that its naturalfrequency is on the order of 100 kilocycles. The crystal is enclosed ina suitable casing 17 which is resiliently held in position within theshaving head of any suitable meanssuch as one or more leaf springs 20..The forward portion of the casing adjacent the driving edge 130i the"blade 7 is provided with a channel member 21 into which is fitted thedriving edge of the blade; thus, the blade is vibrationally coupled tothe crystal.

The crystal frequency of 100 kc. is stated for illustra tive purposesonly. According to my inventionthe blade may be driven by a crystal orother suitabletransducer having a vibrational frequency or frequencieswithin a range extending from approximately 100 kc. upwards toapproximately 4 megacycles. I have found thatthe hair severing actiondescribed. above as characteristicof this invention predominates. withinthis range and may even persist to a lesserextent at frequencies beyondthis range.

As is shown in FIG. 3, I provide in the handle 2 a v void 22 in which islocated ahigh-frequency generator 23.

of any suitable design capable of producing alternating voltages at theresonant frequency of the crystal 16. The generator is designed to beenergized by a commonly available source of power such as by batteriesor by a 110 volt, 60 cycle electrical source which is connected to theinput of the generator through a line cord 24. The output of thegenerator is connected to the crystal through the leads 25 which passfrom the void 22 upward through a passage 26 in the handle 2 and intothe space between the upper plate 3 and the lower plate 4 where theleads are connected to appropriate connections 27 on the crystal 16.

Referring now to FIG. 10, there is shown a schematic diagram of anelectrical circuit comprising a power source or high frequency generator23-, which in this case, is in the form of a battery powered inverter.This unit 23 comprises a small size, high frequency transformer core 32having a primary winding 33, a feedback winding 34, and an output orsecondary winding 35. Two leads 25 extend to either side of apiezoelectric element 16, which in this case is a lead zirconate-leadtitanate ceramic material, having a width of about one quarter of aninch, a length of about one half an inch, and a thickness of about onequarter of an inch.

I used a piezoelectric ceramic which had a principal mode of vibrationin the longitudinal extensional mode, namely a so-called PZT-4 crystal,obtained from the Clevite Corporation, of Bedford, Ohio. Other devicesmay be used, such as other ceramics, lead titanate crystals, bariumtitanate crystals, ammonium dihydrogen phosphate crystals, Rochellesalt, ethylene diamine tartrate, di-potassium tartrate, tourmaline, andlithium sulfate.

An output alternating voltage of 100,000 cycles per second, for example,is impressed across the element 16, as will now be described, forcausing vibrational longitudinal extension of the element 16.

The primary winding 33 of the generator or inverter 23 is center tappedat 36, and connected to a 2.5 volt positive terminal of a battery orother D.'C. source 37. A filter capacitor 38 is connected in parallelwith the DC. source 37. The negative voltage lead 39 is split andconnected to the collectors 40, 41,.respectively of transistors 42, 43.The bases of the transistors 42, 43 are connected to each otherthroughthe feedback winding 32, which is inductively coupled to the core32, while the emitters of the transistors 42, 43 are connected to eachother through the primary winding 33. Thus, in operation, an oscillatingcurrent. is impressed on the core 32, and is coupled to the outputwinding 35. The lead 39 from the negative side of the DC. source 37, inaddition to being connected to the transistor collectors, is alsoconnected at 44 to the center tapped feedback winding 34, with aparallel R-C network comprising a resistor 45 and. a capacitor 46connected at 47, 48 into the line 39. The values of the capacitors 38,46 are selected to provide proper filter action and a desired resonantfrequency; for example capacitor 38 may have a 2 microfarad rating andcapacitor 46, a 0.5 microfarad capacity. Using 2N 2912 transistors, forexample, a satisfactory inverter is Obtained, which operates at 100,000cycles and above. If a battery 37 is. providedas shown, the cord 24.shown in FIG. 3, forexample, may be eliminated. If desired, however,rectified alternating current (A.C) may be supplied throughthe cord 24,or A.C. may be supplied and rectified in a conventional, knownmannerbefore being fed to the inverter.

FIG. 8 shows a lead zirconate-lead titanate ceramic piezoelectrictransducer 16, and illustrates the mode of vibration thereof. The normalposition is shown in heavy lines, with the longitudinally extended,diminished thickness form shown in phantom lines. As the alternating.

voltage or polarity is impressed on this transducer; it changes between,these forms at the frequency of the impressed "voltage; r

In another embodiment, it may be desired to have some portions of thepower source or the entire power source, located remote from the handleportion 2 as well as remote from the shaving head 1.

In such a case, I have successfully operated the unit with an oscillatorgenerally known as a General Radio Company oscillator Model 1210-C, theoutput signal of which may be fed to a tube type amplifier, such as aGeneral Radio model 1233-A amplifier, before being fed to the crystal orother transducer 16.

Such a type 1210 oscillator has a frequency range of 20 to 500,000cycles per second, and is a series-parallel,

resistance-capacitive network type oscillator, the exact design of whichis shown and completely described in a booklet entitled OperatingInstructions, Type 1210-C Unit, RC Oscillator, (Form 1210-l0O-H), datedAugust 1964, published by the General Radio Company, West Concord, Mass.Likewise, a booklet entitled Operating Instructions, Form l233-0l00E,dated April 1965, and published by General Radio Company, describes ingreat detail the type l233-A power amplifier, which is basically a threestage push-pull electron-tube type amplifier.

In the electromechanical transducer art, it is well known that, inaddition to fundamental resonant vibrational frequencies, the crystalsor other transducers have various harmonics which are low numericalintegral or fractional multiples of the fundamental frequencies.Although I prefer that the vibrations of the crystal occur at thefundamental frequencies thereof, it is not necessary that they so occur.

FIGS. and 6 illustrate an alternative embodiment of the invention inwhich a blade 7 is mounted in the head of the razor and clamped betweena fulcrum ridge 14 on the lower plate 4 and the forward edgeof the upperplate 6 as in the embodiment shown in FIGS. 1 to 4. Similarly, a bladedriving piezoelectric crystal 16 is mounted in the rearward portion ofthe cavity in the shaving head and is resiliently supported in thisposition by a leafspring 20. In this modification the efiiciency of thevibrational coupling between the crystal: 16 and the driven edge 13 ofthe blade is greatly enchanced by the provision of a mechanicaltransformer 28. The transformer may be made of any suitable materialsuch as metal .or plastic which is sufficiently rigid at the drivingfrequency of the crystal to transfer substantial energy to the blade 7.

Referring now to the operation of these razor units, it should beunderstood that, in the embodiment shown in FIGS. 3, 5, and 6, thefunction of the transformer means 28 is to gather energy from thecrystal and impart the energy to the blade. Thus, the rear face of thetransformer 30 is much larger than the forward face 31 thereof, and theshape of the transformer 30 is such that energy is concentrated beforebeing imparted to the blade.

Although the exact reasons for the operation of this unit are not knownwith certainity, it is believed that the blade itself does notordinarily, and certainly does not necessarily, vibrate with exactly thesame vibrational characteristics as the crystal. Thus, the entire bladeis notnecessarily moved solely longitudinally, forwardly and 'backwardlyalong its length at the frequency of, and with the amplitude of, thecrystal or ceramic transducer. It is believed that longitudinal wavesfed into the back edge of the blade travel toward the front edge, butare at least partially reflected back into the blade when tending toleave the blade. When the Waves reach the beveled edge portions of theblade, reflections thereof occur, and cause a change in wave pattern toa shear effect. The geometry of the blade edge is such that these wavesare collected at the edge of the blade, and the low mass blade edge isactivated with considerable energy, although not necessarily energy fromsynchronous movement of the entire blade back and forth at thefundamental frequency of the transducer. Obviously, the resilience,strength, andother characteristics of the material comprising the blade,as well as the .exact geometric shape thereof, determine the exactbehavior thereof. However, it is not a necessary part .of the inventionthat the blade itself vibrate in any exact mode, only that the energysupplied thereto is vibrational ultrasonic energy of the type referredto herein.

Referring now to the ridge 14, the groove15, and the forward edge 6 ofthe upper plate 3, used to hold the blade 7 in position, the linedefined by the groove 15 should be at a vibrational mode. However, it isnot a necessary part of the invention that the blade itself vibrate inany exact mode, only thatthe energy supplied thereto is vibrationalultrasonic energy of the type referred to herein.

Referring now to the ridge 14, the groove 15, and the forward edge 6 ofthe upper plate 3, used to hold the blade 7 in position, the linedefined by the groove 15 should be at a vibrational node. However, it isnot necessary, for reasons which are not understood with certainty, thatthe node be predetermined, calculated .or empirically located, in allcases, since it has been, discovered that holding or supporting theblade in the manner described may actually serve to create a node atthat point. In other words, a blade in contact with a member havingultrasonic driving energy can be made to have various apparently naturalresonant frequencies, and holding or supporting it in a particular waywill be one of the factors which determine such fundamental .or naturalresonant frequencies, or overtones or undertones thereof.

Referring now to FIGS. 7 and 9,, a further alternate construction isshown, in which the transducer comprises a pair of crystal units 49, 50,adhesively attached to each other to form a unitary piezoelectrictransducer having .a fiexural mode of vibration. A. mechanicaltransformer .51 attached to the upper end of the transducer supports ablade 52, which is disposed with a cutting edge portion 53 thereofspaced apart from the guard 54. Leads 55 supply an alternatingrvoltagefrornthe power source, such,

In other details, the razor. is similar to those shown in FIGS. 3 and 5,for example. The type of power supply is also optional in this case; aninverter powered by a DC. source, or an oscillator-amplifier combinationmay be used, for example.

In the operation of this unit, the alternating voltage causes a faceshearing or transversely expanding action in each crystal, and theresult is a deflection or fiexural action at the free end of thecomposite transducer. This composite transducer creates a higheramplitude, lower force type motion than a single element transducer; Inthis construction, a single element crystal having a flexuralvibrational mode may be substituted for the composite unit. Thevibrational energy of the transducer, in operation, is supplied to theblade, and the vibratory action of the blade is. substantially the sameas that described in relation to the other embodimentsof the invention.

The phantom lines in FIG. 9 show the vibrational mode of the transducerunder the influence of an applied alternating voltage. The materialswhich comprise the.

The transducers used for producing longitudinal extension.

were typically so-called 0 X-cut materials (major face cut perpendicularto the X-crystallographic axis, edges parallel to Y and Z axes). For theelements of the transducer vibratory in the face shear mode, a so-calledDT.

, cut orSL cut is appropriate suchfcutsbeing well kno'wn to thoseskilled in the art of piezoelectric crystals.

The configuration of the mechanicaltransformer .is

best seen in the perspective view of FIG. 6. In cross section thetransformer tapers from a relatively thickporcrystal to a thin sectionat the forward edge 31 where the transformer couples to the driven edge13 of the blade.

It would, of course, be possible to drive the blade by other transducermeans such as a magnetostrictive device in .place of the; piezoelectriccrystal, provided-that the.

driving means is capable of oscillating within the range of frequenciescontemplated by the invention. Typical magnetostrictive device areferrite materials of many sorts, particularly those of an E-core shapewith legs thereof inductively wound with coils having an ultrasonicoutput frequency.

As previously pointed out, prior inventors have attempted to providemechanical and electromechanical drives for the cutting edge of a safetyrazor but these have not been successful because the mechanism ofcutting hair was apparently not fully understood and the drivingfrequencies which were tried by the prior art workers were too low bymany tons of thousands of cycles. In accordance with my invention, thefrequency at which the blade edge is driven must be within the range ofapproximately 100,000 cycles per second upwards to approximately 4million cycles per second with the desirable effect persisting to alesser extent beyond this range. Once the art is informed of thisrequisite, it then becomes apparent why I have mounted the blade 7 inthe particular manners shown in FIGS. 3 and 5.

The clamping of the blade along a line intermediate its cutting edge andits driven edge is one good means for decoupling the blade from theshaving head. This accomplishes two things. First, the vibrationalenergy is not transferred to the shaving head and, second, the restrainton the vibration and oscillation of the cutting edge of the blade isminimized. The ideal position at which the blade should be clamped is,of course, at a vibrational node between the cutting edge and the drivenedge of the blade. In general a node will occur an integral multiple ofa half wave length from the driven edge of the blade. The place at whichthe blade is clamped will depend on the resonant properties of the bladeitself and upon the frequency at which the crystal drives the blade.Taking into consideration these and other relevant factors such as thedistance between the cutting edge and the driving edge, it will beapparent to those skilled in the art of vibrational systems that in anygiven system, there may be one or several nodal lines along which theblade may be clamped. Moreover, in some systems and using particularcrystals, a designer may couple the driving crystal to the blade in sucha way that the blade is effectively operated at a harmonic frequency ofthe crystal rather than at its fundamental frequency.

By the term ultrasonic as set out in the specification and claimshereof, it is intended to be meant frequencies which are not only wellabove so-called audio frequencies, that is, frequencies up to about20,000 cycles per second but also frequencies greatly in excess of suchfrequencies, the term ultrasonic being intended to include frequenciesup to 4 or 5 megacycles .or more, such frequencies in various other artsbeing sometimes referred to as radio frequencies, intermediatefrequencies and very high or ultra-high frequencies. These and othervariations are intended to be within the scope of my invention which isdefined in the following claims.

I claim:

1. A razor unit comprising, in combination, razor head means, bladeguard means associated with said head means, electromechanicaltransducer means disposed at least partially within said head means andsupported therein so as to allow ultrasonic vibrational movement of atleast a part thereof in response to an alternating voltage impressedthereon, cutting means mechanically coupled to a portion of saidtransducer means, said cutting means including a cutting edge portionthereon, said cutting edge portion extending at least partiallyoutwardly of said razor head means, and power source means electricallyconnected to said transducer means for impressing an alternating voltagethereon at an ultrasonic frequency, whereby, upon operation of saidpower source means, said transducer means vibrates at an ultrasonicfrequency, and transfers vibrational energy to said cutting means.

2. A razor unit as defined in claim 1 in which said transducer means andsaid power supply means are operable at a frequency of from about100,000 cycles per second to about 4,000,000 cycles per second.

3. A razor unit as defined in claim 1 in which said transducer meanscomprises a piezoelectric ceramic material.

4. A razor unit as defined in claim 1 in which said transducer meanscomprises a piezoelectric crystal.

5. A razor unit as defined in claim 1 in which said transducer meanscomprises a magnetostrictive element.

6. A razor unit as defined in claim 1 in which said cutting meanscomprizes razor blade means, and in which said razor blade means issupported along a line parallel to said cutting edge portion, said linelying intermediate said cutting edge portion and the edge portion ofsaid blade means which is opposite said cutting edge means.

7. A razor unit as defined in claim 1 which further includes handlemeans thereon, and in which said power supply means comprises anelectronic inverter unit disposed within said handle means.

8. A razor unit as defined in claim 1 in which said power supply meanscomprises electronic oscillator means having a normal output of anultrasonic frequency, and an electronic amplifier means for amplifyingthe output of said oscillator means.

9. A razor unit as defined in claim 1 in which said transducer meanscomprises a composite piezoelectric unit having two elements thereoffastened together, said elements having similar modes of vibration, andwherein said piezoelectric unit is held at one end thereof, is free tovibrate fiexurally at another end thereof, and wherein said cuttingmeans is mechanically coupled to said composite piezoelectric unit.

10. A razor unit as defined in claim 1 which further includes mechanicaltransformer means for coupling said cutting means to said transducermeans.

11. A razor unit as defined in claim 3 in which said ceramic material isa lead zirconate-lead titanate material having a longitudinalvibrational mode for imparting energy to said cutting means at anultrasonic frequency.

References Cited UNITED STATES PATENTS 1,158,741 11/1915 Stearns 30-452,230,630 2/ 1941 Sperti 30-45 2,232,271 2/ 1941 Rider 3045 2,834,1585/1958 Petermann 3108.2 2,972,069 2/1961 Sproule 310-8.3 3,008,23211/1961 Shea 3045 3,074,034 1/1963 Crownover 3l0-9.6 3,191,913 6/1965Mettler 310- 8.2

OTHELL M. SIMPSON, Primary Examiner

